Optimization of rotor shape for constant torque improvement and radial magnetic force minimization

The design of notch and barrier was optimized in order to improve the characteristics of constant torque while minimizing the cogging torque that occurs as a result of teeth and slot structure. The barrier was installed in order to minimize the cogging torque and torque ripple by finite element method (FEM) with a reduced barrier width toward the center of magnetic pole. The position and width of notch, which can offset cogging torque, can be calculated with energy distribution of air-gap using Fourier series. The optimized model demonstrates a 60% decrease in the cogging torque, a 75.3% decrease in the torque ripple and a 3% increase in the operating torque when compared with the basic model.     

静电冷却技术对钛合金摩擦磨损性能的影响

为了更好地将静电冷却技术应用到钛合金的车削中,在自行设计的高速摩擦磨损试验装置上,进行了YG8/Ti6A14V摩擦副的摩擦磨损试验.结果表明:静电冷却技术可以有效地降低YG8/Ti6A14V摩擦副间的摩擦系数,在抑制摩擦副磨损的同时还可以改善Ti6A14V磨损表面质量.扫描电镜分析表明,硬质合金高速摩擦时的磨损机理以粘...     

含移动铰平面连杆机构动态静力分析键合图法

阐述了建立含有移动铰的平面连杆机构键合图模型的一般方法.将运动副约束反力视做未知势源加在系统键合图模型相应的0-结处,不能完全消除系统键合图模型的微分因果关系.在考虑混合因果关系情况下,推导出便于计算机自动生成的系统驱动力矩及运动副约束反力方程的统一公式,克服了微分因果关系及非线性结型结构给计算机自动进行系统动态静力分析所带来的代数困难.所述方法特别适合于多能域并存的系统,通过实例说明本文方法的有效性.     

机床滚珠导轨中圆柱面-球面结合面静特性分析及试验研究

为了研究直线滚动导轨磨损退化对导轨各参数的影响,考虑了每个滚珠的受力、变形和初始预紧力,推导和计算了与磨损退化有关的刚度退化模型、预紧力退化模型、接触角变化模型、摩擦力和摩擦因数模型、最大蠕滑率和临界载荷模型.直线滚动导轨滚珠与滚道的磨损伴随着直线导轨的刚度和预紧力产生退化.同时,上排和下排的滚珠接触角、临界载荷、摩擦因数、摩擦力、最大蠕滑率等参数也发生变化.以上参数对滚动导轨的性能具有重要意义,但这些参数很难直接通过试验测量得到.以国产某型号滚珠直线导轨为研究对象,对所建立的各模型进行仿真分析.结果表明：直线滚动导轨磨损退化对导轨各参数均有不同程度的影响,通过测量直线滚动导轨轨道的磨损可以有效预测导轨各参数的变化规律.

     

静动组合荷载下混凝土高温后的双轴动态力学性能

由于试验的复杂性,高温后混凝土在复杂应力状态下的动态力学性能研究一直较少,但在建筑物火灾和国防军事防护工程中,混凝土结构多处于多轴应力和冲击荷载的共同作用下.为研究静动组合荷载下混凝土高温后双轴动态力学性能,采用真三轴静、动力综合加载试验系统,使用真三轴试验机预先施加双轴轴压,再利用SHPB试验装置,分别对常温(25℃...     

Effects of the types of overlap on the mechanical properties of FSSW welded AZ series magnesium alloy joints

The effects of the types of overlap on the mechanical properties of the friction stir spot welding(FSSW) welded AZ series magnesium alloy joints were investigated by microstructural observations,microhardness tests,and tensile tests.The results show that the micro-structure of the stir zone adjacent to the periphery of the rotating pin is mainly composed of the upper sheet.The average distance D between the longitudinal segment of the curved interface and the keyhole periphery,the tensile shear force,and the microhardness of the stir zone of the FSSW welded AZ61 alloy joint are the highest in all samples.During FSSW of AZ31 and AZ61 dissimilar magnesium alloys,the ir-regular deformation of the longitudinal segment of the curved interface appears,while the microhardness of the stir zone is higher when AZ61 alloy is the upper sheet.Moreover,the microhardness of the stir zone increases initially and then decreases sharply in the longitudinal test position.     

双层预紧式六维力传感器动态性能的理论与实验研究

对一种新型的双层预紧式六维力传感器进行了动态性能理论分析与实验研究。首先介绍了双层预紧式六维力传感器的结构特点。建立了该传感器的振动系统简化模型,基于螺旋理论和多自由度系统振动学推导了系统的运动微分方程。经过对运动微分方程进行求解,得到了传感器的各阶固有频率。最后采用阶跃响应法对传感器样机进行动态性能实验研究,经过快速傅里叶变换得到了传感器的频率响应曲线。实验结果与理论计算结果一致,从而验证了理论推导的正确性。研究结果表明,双层预紧式六维力传感器的动态性能较好,能够满足一般工业生产中对六维力测量的要求。     

Effects of bioleaching on the mechanical and chemical properties of waste rocks

Bioleaching processes cause dramatic changes in the mechanical and chemical properties of waste rocks,and play an important role in metal recovery and dump stability.This study focused on the characteristics of waste rocks subjected to bioleaching.A series of experiments were conducted to investigate the evolution of rock properties during the bioleaching process.Mechanical behaviors of the leached waste rocks,such as failure patterns,normal stress,shear strength,and cohesion were determined through mechanical tests.The results of SEM imaging show considerable differences in the surface morphology of leached rocks located at different parts of the dump.The mineralogical content of the leached rocks reflects the extent of dissolution and precipitation during bioleaching.The dump porosity and rock size change under the effect of dissolution,precipitation,and clay transportation.The particle size of the leached rocks decreased due to the loss of rock integrity and the conversion of dry precipitation into fine particles.     

深海通海阀开启力仿真与试验

阀门的开启力是阀门强度设计的重要依据,同时也是阀门启闭控制系统设计的基础。针对先导式深海通海阀的开启力变化规律,分别运用仿真与试验的方法对所研究的深海通海阀在开关阀过程中阀杆受力的变化规律,以及有无先导孔条件下开阀力大小进行了研究,得到了相关规律及开阀过程中最大开阀力值。研究结果表明,先导孔在整个开阀过程中能减少开阀力,并且有先导孔结构开阀力变化更平稳。所得结论及试验方法对于该型先导式通海阀研究具有重要的参考意义。     

板式换热器触点分布对换热阻力性能的影响

为进一步提升人字形板式换热器的综合性能,对其触点分布进行研究,得到触点分布与下层波峰线到板换长度方向对称轴的距离L的关系式。通过数值模拟,分析人字形板式换热器单流道模型L改变时,换热和阻力的变化情况。随着L的变化,第一层触点位置周期性变化,压降与Nu数均呈现周期性变化,在半周期位置获得最小值;面积质量因子j／f的变化也呈现周期性,趋势和压降、Nu数变化相反,由于流场分布的均匀程度不同,j／f在半周期位置获得最大值。触点分布对换热阻力的影响,随着Re的增大而逐渐增大。结果表明:选择L为半周期时,可以在板式换热器的3个基本参数不变的情况下,进一步提高板换的综合性能。     

Variation of vertical and horizontal drilling rates depending on some rock properties in the marble quarries简

The main objective of this study is to determine the rates of vertically and horizontally oriented drilling processes in marble quarries and to observe the factors affecting the drilling rates in terms of physical and mechanical properties of the rocks. In situ drilling tests were performed in different marble quarries with different marble types and drilling times and penetration rates for a series of successive depth-increments were trying to be determined under vertically and horizontally oriented conditions. In order to understand the relation between the parameters that are investigated within the scope of this research, uniaxial compressive strength, Brazilian tensile strength, impact strength, Bohme abrasion strength, P-wave velocity, porosity, unit volume weight, Schmidt hardness index and brittleness index values were correlated with the drilling rates. It was noticed that the porosity and unit volume weight could be taken as the key parameters among them for obtaining meaningful correlation with drilling performance. It was also observed that the physical and mechanical rock properties are more relevant in vertical drilling than horizontal drilling.     

髋臼力和肌肉力对股骨有限元分析结果的影响

建立基于CT影像的股骨有限元模型,研究髋臼力和各个肌肉力对有限元分析结果的影响.对于完整股骨模型(模型I),施加髋臼力和各种肌肉力并计算.对于股骨近端模型(模型II),施加相同大小不同作用面积的髋臼力并计算.通过对计算结果的分析表明,臀中肌肌肉力对股骨内应力分布影响最大;髋臼力的作用面积越大,模型各单元应力越小,施加载荷位置的单元此趋势尤为明显.可以为大量个体化有限元计算预测股骨强度提供载荷简化的主要依据.     

C60高性能粉煤灰混凝土配制及性能的研究

介绍了Ｃ６０高性能粉煤灰混凝土的配合比选择,提出了抗压强度公式．也对粉煤灰混凝土的力学性能和耐久性进行了试验和探讨．     

玻璃纤维的含量对复合材料的力学性能影响及表征研究

为研究不同质量分数的玻璃纤维对增强聚丙烯复合材料力学性能的影响,选择直径为10μm的玻璃纤维制备复合材料小样.测试在不同质量分数时材料的拉伸强度、弯曲弹性模量等力学性能,并应用扫描电镜(SEM)对其微结构进行表征.结果表明:玻璃纤维质量分数对复合材料的取向分布有很大影响,随着玻璃纤维质量分数增加,拉伸强度增大,但弯曲弹性模量、弯曲强度变化不明显.此外,随着质量分数的增加,复合材料的脆性变大;SEM分析表明复合材料中玻璃纤维有一定的取向且分布相对均匀,玻璃纤维和复合材料基体结合良好.     

Effects of heat treatment on the microstructures and mechanical properties of a new type of nitrogen-containing die steel

Nitrogen can increase the strength of steels without weakening the toughness and improve the corrosion resistance at the same time. Compared with conventional nitrogen-free die steels, a new type of nitrogen-containing die steel was developed with many superior properties, such as high strength, high hardness, and good toughness. This paper focused on the effects of heat treatment on the microstruc-tures and mechanical properties of the new type of nitrogen-containing die steel, which were investigated by the optimized deformation process and heat treatment. Isothermal spheroidal annealing and high-temperature quenching as well as high-temperature tempering were ap-plied in the experiment by means of an orthogonal method after the steel was multiply forged. The mechanical properties of nitro-gen-containing die steel forgings are better than the standard of NADCA #207-2003.     

回火温度对高强度容器钢组织结构与性能的影响

通过回火试验,研究了回火温度对高强度容器钢组织结构与力学性能的影响。研究表明：在550～670℃范围内,随着回火温度升高,钢板抗拉强度和屈服强度先增大后减小,延伸率和冲击韧性先减小后增大,这源于索氏体组织和碳化物的共同作用。     

Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels

Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels were studied.To investigate the microstructure and mechanical properties,optical microscopy,scanning electron microscopy,X-ray diffraction,tensile test,and hardness test were used.The results show that the solution-annealing treatment in the cold-rolled steel redounds to the formation of submicrocrystalline Fe2(Mo,Ti)Laves phase particles,which are stable at high temperatures.These secondary Laves phase particles prevent from recrystallization at high temperatures and correspond to semi-brittle fiacture in the subsequent aging treatment.     

Effect of high temperature and high strain rate on the dynamic mechanical properties of Fe-30Mn-3Si-4A1 TWIP steel

The dynamic mechanical properties of Fe-30Mn-3Si-4A1 twinning induced plasticity （TWIP） steel were studied by the split-Hopkinson pressure bar （SHPB） at temperatures of 298-1073 K and strain rates of 700, 2500, and 5000 s-1. The TWIP steel indicates strain rate hardening effect between 700 and 2500 s-1, but it shows strain rate softening effect between 2500 and 5000 s-1. In addition, the strain rate softening effect enhances with an increase in deformation temperature. After deformation, the microstructures were studied by optical microscopy （OM）. It is shown that the deformation bands become more convergence, a part of which become interwoven with an increase in strain rate, and the dynamic recovery and recrystallization are enhanced with an increase in both temperature and strain rate.     

Effect of fast cooling rate on the microstructure and mechanical properties of low-carbon high-strength steel annealed in the intercritical region

The effect of fast cooling rate on the microstructure and mechanical properties of low-carbon high-strength steel annealed in the intercritical region was investigated using a Gleeble 1500 thermomechanical simulator and a continuous annealing thermomechanical simulator. The results showed that the microstructure consisted of ferrite and bainite as the main phases with a small amount of retained austenite and martensite islands at cooling rate of 5 and 50 ℃/s, respectively. Fast cooling after continuous annealing affected all constituents of the microstructure. The mechanical properties were improved considerably. Ultimate tensile strength(UTS) increased and total elongation(TEL) decreased with increasing cooling rate in all specimens. The specimen 1 at a cooling rate of 5 ℃/s exhibited the maximum TEL and UTS×TEL(20% and 27 200 MPa%, respectively) because of the competition between weakening by presence of the retained austenite plus the carbon indigence by carbide precipitation, and strengthening by martensitic islands and precipitation. The maximum UTS and YS(1 450 and 951 MPa, respectively) were obtained for specimen 2 at a cooling rate of 50 ℃/s. This is attributed to the effect of dispersion strengthening of fi ner martensite islands and the effect of precipitation strengthening of carbide precipitates.